1. Field of the Invention
The present invention relates to a power steering device for car utilizing a pair of control cables to be put under a tensile force and a power cylinder.
2. Description of the Prior Art
A shaft has generally been employed as means serving to transmit a rotational motion of the steering wheel to the steering mechanism and recently use of a flexible control cable has been examined in view of its various advantages such that a high degree of freedom is available for location as well as angle at which the steering wheel is mounted, a wide space is obtained around a driver's feet, the control cables can be selectively laid within the engine room and the cable replacing the shaft contributes to the desired weight reduction.
The control cable can be selected from those of various types and it is preferred to use a pair of pull-cables adapted to be subjected only to a pulling force in view of disadvantages encountered by the cables of other types such that so-called push/pull-cable can not be free from an undesirable play generated on its pushing side which may cause a transmission delay and an error, the geared cable having a single wire spirally wound therearound and serving as engaging teeth requires an extremely high precision with which the single wire is wound around the cable in order to avoid the play and consequently requires unacceptably high manufacturing cost and rotary cable also can not be free from the transmission delay and the error due to its insufficient torsional rigidity.
The steering device using said pull-cable is described in Japanese Utility Model Application Disclosure Gazette No. 1974-11432. However, this steering device of prior art comprises a bobbin coupled to a steering wheel, a disc coupled to tie rods on either side and a pair of pull-cables connecting said bobbin to said disc which must be placed halfway between said tie rods on opposite sides. Accordingly, no freedom is available for design and it is difficult for such steering device to be placed in a restricted space.